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Rechargeable Torch Light repair

Thread starter #21
Hi Les Jones

Can I put zener diode at C2?
I've marked with yellow rectangular.
Is it correct polarity? or it can be put any polarity?
IMG_20171124zener.jpg

What voltage should I use?
 
Last edited:

Les Jones

Well-Known Member
#22
A zener in parallel with C2 is a good way to limit the voltage. Either a 12 volt or 15 volts zener should be OK. It should be at least 2 watts power rating. You have the polarity correct. I think you should also raplace C1 as it could be breaking down as JimB suggested. I would reccomend a capacitor rated at above 250 volts AC (Rather than the 400 volt DC rating.) and X rated. (This indicates that thay are safe for this sort of application.) I think this capacitor is 1.5 uF from the 155j in the part number.

Les.
 
Thread starter #23
A zener in parallel with C2 is a good way to limit the voltage. Either a 12 volt or 15 volts zener should be OK. It should be at least 2 watts power rating. You have the polarity correct. I think you should also raplace C1 as it could be breaking down as JimB suggested. I would reccomend a capacitor rated at above 250 volts AC (Rather than the 400 volt DC rating.) and X rated. (This indicates that thay are safe for this sort of application.) I think this capacitor is 1.5 uF from the 155j in the part number.

Les.
I've replaced the C1 with CL21 105k 250v (printed on) that one from the right circuit.

View attachment 109406

That circuit is also from the rechargeable torch light with FM radio. Radio is not funtion and I took from that.
After replacing the out put is still the same. Without load 80V and with load 10V or 12V. But C2 will explode within 5minutes.
That's why I'm planning to put zener.

Can u please give me suitable C1 part number?
 

Les Jones

Well-Known Member
#24
Either of these capacitors would be a suitable replacement for the original 1.5 uF capacitor. This would give a charging current of about 100 mA which in my opinion would be too high. This is only a guess as you have not given the full specifiication of the battery. If you used a 4.7 volt zener diode this would would limit the charge voltage to a more suitable level. (A 1 watt rating for a 4.7 volts zener should be enough.)

Les.
 
Thread starter #26
Hi Les Jones ,
I couldn't get what u recommended. The shop gave me the below C that can use (what they said) .
IMG_20171221_112454.jpg
And I only manage to get 5.1 zener.
So I decided to give a shot with old C 105k.
After put the zener , there u go , output v is 6.2 with load.
7.4v when I put the C 155j.
That means if the C1 capacitance is higher output v is higher.
Should I use 224k C?
 

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